Studies show that vestibulo-ocular reflexes can use qualitatively different processing mechanisms than vestibular perception. Given this, it is not surprising that vestibular symptoms correlate poorly with reflexive measures. Yet, quantitative clinical assays of motion-evoked perception are seldom, if ever, performed. Instead, clinicians primarily assay vestibular perception via patient histories, which may help explain why the underlying cause of perceptual symptoms often goes undiagnosed. It has been reported that roughly 30% of patients reporting symptoms of dizziness or disorientation receive an uncertain diagnosis and/or a diagnosis that is unconfirmed by measurements or signs. We reason that quantitative perceptual tests can contribute to our ability to diagnose patients. More specificall, because of high sensitivity and specificity, perceptual thresholds provide a common way to evaluate sensory function clinically (e.g., audiogram), so measuring vestibular thresholds may provide a new diagnostic toolkit that will help diagnose both central (e.g., vestibular migraine) and peripheral (e.g., Meniere's disease) vestibular dysfunction using a single common methodology. In fact, vestibular thresholds mimic the audiogram test of hearing; this takes advantage of clinician experience with audiograms and helps make vestibular threshold interpretation straightforward. We have previously reported measureable threshold differences among various patient classes and normal subjects. These results suggest that thresholds provide graded quantitative measurements that can help confirm a diagnosis (perhaps obviating the need for additional rule- out testing) or guide new and/or more refined diagnoses. Furthermore, we have developed automated procedures that reduce test times dramatically. These advances, alongside data analysis improvements, allow us to measure perceptual thresholds across a broad range of conditions in less than 2 hours. We propose to recruit qualifying MEE patients suffering episodic vestibular symptoms to participate in threshold testing, alongside other standard clinical measures like the VOR We specifically propose to evaluate the diagnostic power of threshold testing and existing clinical tests quantitatively - bot individually and when combined - using standard statistical approaches. To provide normative data that is both age and gender-matched, we also propose to measure thresholds in healthy normal subjects between the ages of 18-80.